In general, vacuum processing chambers for processing substrates include a substrate transfer opening, commonly known as a slit valve. A slit passage associated with the slit valve is commonly used to transfer substrates into and out of the processing chamber between processing cycles. Commonly a robot extends from a cluster tool through a slit valve opening through the slit valve passage to deliver or remove a substrate to be processed to or from a processing location in the vacuum processing chamber. Once the substrate transfer at the substrate processing location is complete, the robot is retracted through the slit valve opening and back into the cluster tool. The slit valve opening is commonly sealed at an outside surface of the chamber body by a blocking plate which moves over the slit valve opening, in a coordinated motion with the movement of the robot and substrate into and out of the processing chamber. Plasma is often used in a processing chamber to enhance the process being performed. In a typical arrangement of a vacuum processing chamber, where a plasma is utilized to initiate or enhance process activity, the processing chamber and all internal services exposed to the plasma and the chemical by products are affected and can become coated with chemical byproducts of the process being performed.
Typically, the walls of the processing chamber are at least several inches thick to provide a sturdy chamber wall for processing activity. Thus, the opening in the side of the processing chamber which allows substrates to be transferred into and out of the chamber, the slit valve passage, presents a large tunnel-like opening which creates a geometric discontinuity at the inside surface of the processing chamber. The presence of a large cavity hole (the opening of the substrate transfer passage) adjacent to the space of the central processing location allows the plasma envelope which is present during plasma processing at the substrate processing location to expand into the cavity of the slit valve passage. The expansion of the plasma envelope into the cavity of the slit valve passage creates a distortion in the portion of the plasma situated adjacent to the cavity such that the plasma flux over the substrate in the area near the slit valve passage is affected, such that the deposition or etch taking place in that area is not uniform with other areas of the substrate where such distortion is not present.
Further, the internal surfaces of the slit valve passage, including the inside (process chamber facing side) of the slit valve door, are also subject to deposition and accumulation from the chemical process taking place in the chamber. Deposition on the inside surfaces of the slit valve passage and the slit valve door, require that any cleaning of the chamber (whether wet or dry) extend to include such surfaces. A thorough cleaning of the slit valve door requires that it also be removed so that the full area of the door all the way to the sealing limit be cleaned. In most instances, door cleaning requires that the cluster tool be removed from service so that cleaning of one chamber does not cause potential contaminants from one chamber serviced by the cluster tool to be carried over into a second chamber serviced by the same cluster tool.
The heavy duty sturdy construction of the processing chamber body and its liners finds no ready solution to the problem of the open cavity resulting from the slit valve passageway. Until now there has been no solution to overcome these anomalies of prior art devices, in that all prior doors are constructed in a configuration that gives rise to particles in the processing chamber.